This invention generally relates to a beverage maker and method of brewing beverage by passing hot water through a dry ingredient, such as ground coffee or tea, and, specifically, to an automatic beverage maker of this type.
Beverage makers of the above general type which automatically brew coffee, tea or the like are well known, as illustrated by reference to U.S. Pat. Nos. 1,840,985 of Topper issued Jan. 12, 1932; U.S. Pat. No. 3,511,166 of Bixby, Jr. issued May 12, 1970; U.S. Pat. No. 3,608,471 of Martin issued Sep. 28, 1971; U.S. Pat. No. 3,998,144 of Curtis issued Dec. 21, 1976; U.S. Pat. No. 4,309,939 of Stover issued Jan. 12, 1982; U.S. Pat. No. 4,328,740 of McDonough et al. issued May 11, 1982; and U.S. Pat. No. 4,331,067 of Mysicha et al. issued May 25, 1982.
While the assemblage and structure of parts vary, all such beverage makers have in common certain basic components. The typical commercial sized coffee brewer on the market today, for instance, has a stainless steel or aluminuim, C-shaped housing with base, intermediate and upper sections. The base section has a shelf supporting a removable, portable, metal coffee container, or urn, of approximately 1.5 gallons capacity and a heating element located beneath the shelf for keeping the coffee warm. A metal, funnel-shaped, filter holder is slideably mounted to the upper housing section for receipt of hot water from a dispensing system within the upper section. The hot water seeps through the ground coffee contained with a disposable paper filter within the holder. The hot water is obtained from a hot water supply tank contained within the relatively narrow, upstanding rear housing section which supports one end of the cantilevered upper housing section in position above the base housing section and beverage container. The rear housing section also contains a thermostatically controlled heater for heating the water in the hot water supply tank to a preselected temperature, a sensor for detecting the surface of the hot water in the hot water supply tank, and an inlet valve mechanism. The inlet valve mechanism automatically opens to fill the supply tank with fresh water from a public source of water through a suitable pipe connection when the surface falls below a preselected level.
Opening of the inlet valve results when the hot water level inside the supply tank is lowered below the preselected level by the opening of a solenoid operated, dispenser outlet valve. The dispenser outlet valve is opened when a start switch is actuated to cause hot water to be passed to a spray head, or mixing nozzle. The spray head overlies and dispenses the hot water into the open, relatively wide, circular inlet of the funnel-shaped filter holder, from where it seeps through the grounds to brew the coffee. The freshly brewed coffee then passes out the relatively narrow, open outlet of the holder and into the portable coffee urn.
The dispenser outlet valve is closed a preselected time period after it is opened. Ideally, if the same measured amount of ground coffee is used for each brewing cycle and the time period during which the dispenser valve is open remains the same for each cycle, then the amount of hot water that will seep and the time it takes to seep through the ground coffee during each brewing cycle will be the same. Ideally, the consistency of the coffee for each brewing cycle will then remain the same, cycle after cycle.
Unfortunately, in reality, because most public water supplies contain substantial amounts of minerals and lime which condense out of the hot water to form mineral and lime deposits. These deposits are formed inside the hot water supply tank as well as on the inside surfaces of the dispenser outlet valve, the tubular connection to the spray head end all the intermediate fittings. These deposits form when residual hot water evaporates between brew cycles. These deposits also form when the hot water dispenser valve is closed and because of the repetitive heating and cooling of the water with which it is in continuous contact.
These mineral and lime deposits can form even when the dispensing system is not being used. For instance, formations can result because the hot water level falls when hot water is drained directly from a hot water faucet and cold water is then added to raise the level. Each time this happens, the heating element is energized to again bring the water up to the preselected temperature, and more deposits are formed. Unfortunately, the inlet of the hot water dispenser valve is connected to an outlet of the tank through a dispenser tube which is always in contact with the water. Thus, even when the dispenser valve is closed, it and the dispenser tube are subject to mineral formation.
Depending on the mineral content of the water, the formation of the deposits can grow very gradually, or the free flow of hot water through the dispenser valve and the remainder of the dispenser system up to the spray head, can be restricted in only a matter of weeks or even days. When the cross sectional area of the dispenser valve or dispenser outlet pipe are reduced by formations, the rate of flow, or volume of water which will pass the restricted area during a given time period for a given pressure, will be reduced, since the surface level and thus head pressure in the tank are maintained constant.
Unless the dispenser system is periodically cleaned of these deposits, eventually the amount of hot water which is dispensed over the preselected time period will be substantially less than that needed to fill the urn or to achieve the preselected volume/time ratio required for the best brewing result. The problem of deposits in the dispenser system is exasperated due to the many bends and kinks found in many systems which, together with the uneven deposits, cause varying turbulence that also alters the volume/time ratio of the dispenser system in unpredictable ways. In addition, sometimes the lime deposits will break away from the interior surface of the tank or other components of the dispenser system, and create an emergency by blocking the complete closure of the hot water dispenser valve.
Another problem with some coffee brewers is that the spray nozzles often contain small openings in a head which if clogged with mineral or lime deposits or the like are difficult to clean even after disassembled from the rest of the dispenser system. Consequently, the average user is forced to acquire a regular maintenance service contract to periodically clean the system and to replace parts which cannot be economically cleaned, such as the solenoid operated, hot water dispenser valve at substantial cost. On some units the user can increase the brew time period in order to fill the container despite the reduced flow rate, but in so doing, the quality of the freshly brewed coffee is altered and consistency is lost.
Another disadvantage of known hot water dispenser systems of coffee makers is due to the fact that the hot water dispenser outlet valve is closed not only to the hot water but, also to atmosphere. Accordingly, a separate air vent assembly to vent steam to atmosphere must be provided in the upper portion of the hot water supply tank to prevent the potential build up of explosive steam pressure in the tank. Since the dispenser valve inlet is beneath the normal surface level, a separate overflow system must also be provided.
Many conventional coffee brewers are also provided with a coffee strength control system. The strength control system passes a preselected portion of the hot water from the supply tank to a strength control, or by-pass, nozzle at a location spaced from the spray head, but which overlies a by-pass channel inside the body of the filter holder. Hot water entering the by-pass channel passes the filter and coffee grounds and goes directly into the beverage container to dilute the beverage.
Disadvantageously, known strength control systems are in direct liquid pressure communication with the hot water being dispensed through the spray head. The strength is selectively controlled by means of a manually operated by-pass valve in direct fluid communication with the outlet of the hot water dispenser valve. This strength control, or by-pass, valve can be set in different positions between closed, for full strength, and fully open for a minimum strength brew. Consequently, depending upon the setting of the strength control valve, during the preferred brew time period that the hot water dispenser valve is open, more or less hot water flows into the beverage container, even if there are no problems with mineral and lime deposits. The amount that flows through the spray head remains substantially the same regardless of the strength control setting, while for any strength setting except maximum strength, additional hot water enters through the strength control nozzle.
If the urn is only large enough for the quantity of hot water which is to be drawn when the strength setting is at maximum, strength settings less than maximum can result in a dangerous overflow condition. Thus, if oversized urns are not used, the preferred brew time period during which the hot water dispenser outlet valve is open must be shortened with corresponding decreases in brew strength settings in order to maintain the total quantity of beverage the same for different strength brews.
Due to the location of heating elements in the housing base to keep warm the coffee in the urn, there is no space for the control circuitry and other elements which must be located in the upper housing section. Accordingly, there is little or no room for storage in the upper section. The heating elements are required due to the fact that in known units the urns are made of metal and lack insulation on the inside or even at the top of the urn where temperature and, thus, heat loss are maximum. The containers generally also have a top which is substantially open, so that heat is lost by convection through the loss of steam and vapor as well as by radiation through the sides of the beverage container or urn.
In addition to an A/C power switch, most automatic coffee brewers also have a control switch which disables response to a start brew switch if in an ON position. The operator uses this switch to prevent accidental actuation of the start switch or inadvertent actuation when the water is not up to the preselected temperature. Unfortunately, such switches are unsafely mounted on the outside of the housing where they are both visible and accessible by unauthorized parties.
The base, intermediate upstanding section and upper section of the housings of known commercial sized coffee brewers are generally made separately from numerous parts and then assembled. Consequently, the cost of manufacturing the parts and the cost of assembly are increased while the advantages of a more integral housing design are lost.
In order for cleaning and other maintenance of the hot water supply tank, the tank must be periodically drained. The hot water cannot be drained through the hot water faucet, if the faucet is connected to an inlet adjacent the top of the tank where the water is hottest. Even if the inlet were at the bottom, a separate valve from the faucet is needed to prevent inadvertent draining through the faucet. Accordingly, such hot water supply tanks are drained by means of siphon or a separate sump pump.
Another difficulty with the known brew strength systems of known coffee makers is that the inlet to the by-pass channel and the by-pass channel are formed on the interior of the filter holder by attachment of a by-pass member which distorts the conical filter by holding it away from the conical side of the holder. In addition to the uneven flow through the coffee grounds due to the asymmetrical distortion of the conical shape, such by-pass members are often insufficient to prevent collapse of the filter against the inside conical surface of the brew basket and the resultant partial or whole blocking of the by-pass channel.